Supreme Court Declines to Hear Cases Seeking to Narrow Citizen Suit Enforcement in Federal Environmental Case – Leaving Doors Wide Open

Summary

The Supreme Court declined to hear two key federal environmental enforcement cases, effectively leaving in place lower court rulings that allow for broad private citizen enforcement under the Clean Water Act and Clean Air Act. Because of the Court’s denials, citizen plaintiffs remain free to pursue enforcement cases in the absence of governmental enforcement, thus companies remain at risk of being sued by active watchdog citizen groups.

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On June 30, 2025, the Supreme Court rejected industry petitions to limit the scope of enforcement actions by citizens in two separate cases – one under the Clean Water Act (CWA) and another under the Clean Air Act (CAA). As the Administration becomes more selective in its environmental enforcement efforts, the Supreme Court’s denial of cert in these key cases leaves the door wide open to more federal enforcement citizen suits, including suits to enforce state water pollution control requirements that have a greater scope of coverage than what the federal CWA requires.

The Clean Water Act Citizen Suit

The CWA allows states to administer the National Pollution Discharge Elimination System (NPDES) program so long as state-issued permits comply with federal requirements. Such permits may also include requirements that are more stringent or go beyond those under the CWA.

Port of Tacoma, et al. v. Puget Soundkeeper Alliance, No. 21-35881 (9^thCir. 2024) involved alleged violations of Washington State’s Industrial Stormwater General Permit, which included state law requirements that were greater in scope than the CWA’s requirements. The Ninth Circuit held that environmental groups can pursue a Section 505 CWA citizen suit enforcement action in federal court (33 U.S.C. § 1365) to enforce those state law requirements. The Ninth Circuit’s ruling aligns with decisions from the Fourth and Eleventh Circuits that suggest such private citizen enforcement of state law requirements in an NPDES permit is authorized by 33 U.S.C. § 1365. The Second Circuit, however, does not allow such suits in federal court.

The permittees petitioned the Supreme Court to resolve this split. Notably, the United States weighed in as amicus curiae, urging the Court to resolve the circuit split and arguing that the Ninth Circuit’s decision contravenes the CWA’s text, structure, and context, as well as longstanding EPA regulations. The Supreme Court nevertheless denied cert on June 30, 2025.

The Supreme Court’s denial leaves citizens free to file suit in federal courts outside of the Second Circuit to enforce conditions of state-issued NPDES permits, including those that are broader in scope than what the CWA requires.

The Clean Air Act Citizen Suit

ExxonMobil Corp., et al. v. Environment Texas Citizen Lobby, et al., No. 17-20545 (5^thCir. 2024) involved allegations of excess air emissions from a refinery in the Baytown, Texas area. This case involved the question of standing and whether private citizens could bring Section 304 CAA enforcement actions in federal court (42 U.S.C. § 7604) seeking penalties that would be paid only to the U.S. Treasury. The Fifth Circuit ultimately affirmed the district court’s imposition of millions of dollars in penalties for thousands of CAA violation days, holding that the citizen plaintiffs’ individual members’ injuries were fairly traceable to those violation days.

The Supreme Court’s denial to review the decision means Exxon must pay a $14.5 million civil penalty – believed to be the largest CAA penalty ever awarded in a citizen suit-enforcement action – after 15 years of litigation, including trial and multiple appeals to the Fifth Circuit. The denial also signals that private citizens continue to have standing to seek civil penalties under the CAA that are payable only to the United States government.

The Issue

Federal environmental statutes such as the CWA and the CAA include provisions granting private citizens with authority to bring federal lawsuits for alleged violations.^[1]Plaintiffs can not only pursue civil penalties, injunctive and declaratory relief, but also attorney’s fees, which can be significant if the litigation continues for years. Citizen suits, however, have pre-requisites before suit, including a statutory 60-day pre-suit notice requirement to the companies and federal agencies, giving the companies time to come into compliance or for the agencies to initiate an enforcement action, which would remove jurisdiction for the citizen suit to proceed. These cert denials draw attention to whether the agencies will have the resources to act when faced with increased filings of citizen suits.

Equally important, the Port of Tacoma case means that citizen suit enforcement authority, which is meant to merely supplement governmental enforcement actions, can instead supplant governmental action, because EPA has a longstanding regulation that provides that state law requirements in an NPDES permit that have a greater scope of coverage than what the CWA requires are not part of the federally approved program and thus, are not enforceable in federal court. Thus, citizens can directly enforce requirements that EPA does not enforce in federal courts, even if state water pollution control laws do not contain analogous citizen suit provisions.

Key Takeaways

• The Supreme Court’s recent denials to review and reverse rulings in key environmental lawsuits focusing on the scope of private citizens to bring federal enforcement actions in federal court is substantial.
• These decisions could increase the likelihood that environmental groups will seek to fill the anticipated federal enforcement void under this Administration, especially considering that a significant number of government employees previously tasked with such enforcement actions recently resigned.
• Paying attention to receipt of a Notice of Intent to sue from an environmental or citizen group is the first key step to addressing private federal enforcement actions.
• The next key is to be prepared to timely respond.